A variety of immunostimulatory agents can have unexpected adverse consequences, such as the development ofautoimmune disease or the inmduction of tolerance. We examined the mechanisms responsible for the induction of these adverse consequences. Studies were designed to examine the immunostimulatory cascade initiated by protein antigens (including vaccines) and immunostimulatory CpG motifs present in DNA vaccines on the immune milieu, and whether they predisposed to the development of autoimmunity or tolerance. Ongoing studies indicate that two processes - polyclonal activation of cytokine and Ig producing cells and autoantigen-specific immune stimulation - combine to induce the immune abnormalities found in autoimmune disease states. These effects can be recapitulated by the administration of CpG motifs, such as those present in DNA vaccines. Our experiments show that agents capable of altering the balance between Th1 and Th2 cytokines profoundly impact the initiation, severity and persistence of both systemic and organ specific autoimmunity. For example, diseases characterized by B cell hyper activation (such as SLE, Sjogen's syndrome, and myositis) are characterized by an increased ratio of Th2 : Th1 cytokine producing cells, while diseases such as HIV and Cushing's syndrome are characterized by a decreased Th2 : Th1 ratio. The capacity of gp120-based vaccines and other protein-based immunogens to alter the cytokine milieu and thus contribute to the appearance of lupus-like symptoms was analyzed. Moreover, we showed (using an EAE model) that administration of synthetic oligos expression CpG motifs predisposed to the development of organ specific autoimmunity (thourgh a Th1-mediated, IL-12 dependent process). In research funded by the Office of Women's Heath, we examined the contribution of sex hormones (and agents that modify sex hormone levels) to the creation of an immune milieu conducive to the development of autoimmunity. Current findings suggest that hormones (such as estrogen) induce the activation of Th2 cytokines, thus skewing the Th2 : Th1 ratio to favor the development of systemic autoimmune disease. Our lab is also involved in analyzing the capacity of DNAse to prevent the development of life-threatening glomerulonephritis. In lupus patients, kidney disease results from the deposition of DNA anti-DNA immune complexes. We are studying whether such complexes and/or immunostimulatory DNA molecules, can be eliminated by DNAse treatment. Results from animal experiments suggest that DNAse treatment significantly reduces the activation of IgG anti-DNA secreting B cells over a period of 1-2 months, but then loses efficacy. In studies of the adjuvant-like properties of CpG motifs, we found that such motifs could promote the development of humoral and cell-mediated immunity against the proteins and DNA vaccines with which they were co-delivered.